Detective Inspector Costello has resigned. No notice, no goodbyes. Convinced that George Haggerty murdered his wife and son despite his cast-iron alibi, Costello has gone solo, determined to expose a ruthless killer without being hampered by police protocol. But is she right about Haggerty's guilt? And where has she disappeared to?

DCI Colin Anderson has no time to ponder the loss of his partner of twenty years. With a badly beaten body found on a remote mountain pass; a woman with a serious head wound who won't communicate in any way; and a substantial pool of blood discovered at the edge of Loch Lomond, Police Scotland have their hands full. Could there be any connection to Costello's disappearance ...?